Reproductive isolation between wild and domesticated chaya (Cnidoscolus aconitifolius) in sympatry

Reproductive isolation is a necessary condition for plant domestication in their domestication centre where crops co-occur with their wild progenitors. However, the identification of reproductive barriers and their relative contribution to reproductive isolation have been overlooked in plants under domestication. We assessed pre- and post-pollination reproductive barriers and their relative contribution to reproductive isolation between wild and domesticated chaya (Cnidoscolus aconitifolius) in its domestication centre. We found that wild and domesticated chaya both exhibit a high degree of reproductive isolation. However, the reproductive isolation barriers exhibited some asymmetry: while pre-pollination barriers (differential pollen production and pollinator specificity) were only detected in wild plants, post-pollination barriers (pollen-pistil incompatibility and/or failure to set fruit) were observed in both wild and domesticated plants. We conclude that complete reproductive isolation has evolved in sympatry in co-occurring domesticated and wild chaya.